builtins.c (expand_builtin_memcpy): Add `endp' argument, use it.

builtins.c (expand_builtin_memcpy): Add `endp' argument, use it.

gcc:
	* builtins.c (expand_builtin_memcpy): Add `endp' argument, use it.
	(expand_builtin_stpcpy): New.
	(expand_builtin): Add BUILT_IN_MEMPCPY & BUILT_IN_STPCPY.
	* builtins.def: Add mempcpy & stpcpy support.
	* doc/extend.texi (mempcpy, stpcpy): Document new builtins.

testsuite:
	* gcc.c-torture/execute/string-opt-18.c: New test.

From-SVN: r65551